Generally, this type of light quantity adjustment apparatus is known as an apparatus in which a board having an optical-axis aperture is disposed in a shooting light path (or projection light path), a plurality of light quantity adjustment blades is disposed in the board to be openable and closable so as to make the optical-axis aperture a large diameter or a small diameter, and a quantity of light is thereby adjusted.
For example, Japanese Patent Application Publication No. 2009-020438 (Patent Document 1) discloses an iris diaphragm apparatus in which a plurality of blades is disposed around an optical-axis aperture formed in a board, and opens and closes the light path diameter from a small diameter to a large diameter in similar shapes. It is known that such a diaphragm apparatus has the feature of adjusting a quantity of light in multi-stage with diameters close to a circular shape using a plurality of blades.
The Document discloses an open/close mechanism in which a plurality of diaphragm blades is disposed between a pair of upper and lower ring-shaped boards having an optical-axis aperture at the center, and is opened and closed by a driving unit provided in one of the boards.
Further, Japanese Patent Application Publication No. 2006-322979 (Patent Document 2) discloses an apparatus in which a plurality of diaphragm blades is disposed between boards formed in the shape of a ring, and is opened and closed by a driving unit provided in one of the boards as in Patent Document 1. Such an apparatus is known well that a plurality of blades is disposed around the light-path aperture in the shape of scales, and is opened and closed by a driving unit provided in one of the boards.
Then, in a mechanism for opening and closing a plurality of blades, guide grooves are provided in the board along the trajectory of motion of the blades, pins planted in the blades are fitted into the guide grooves, the blades are rotated in a predetermined direction by a transmission ring provided in the other board, and the motion of the plurality of blades is thereby regulated. In the board for supporting the blades, guide grooves corresponding to the number of blades are disposed around the light-path aperture. The structure of the guide grooves is disclosed in FIG. 4 of Patent Document 1.